Hydraulic cup-shaped tappets with valve clearance compensation elements and inserts for restriction of the oil amount and maintaining the required oil reservoir in the compensation element are known. Document EP 0 443 146 B1 shows a tappet having an insert formed in one piece with the cylinder wall of the cup-shaped housing, resulting in a complicated structure and assembly.
Document DE 36 38 202 A1 discloses a tappet having a hydraulic clearance compensation element and provided with an anti-rotation device by means of a needle roller which partially projects out of the tappet housing and snugly fits in a groove of the machine part that surrounds the tappet and has a bore for guiding the tappet for displacement in an axial direction. This arrangement is however not directed to a cup-shaped tappet but to a differently designed roller tappet.
Document EP 0 187 217 B1 shows a cup-shaped tappet of the afore-stated type which slightly rotates about its longitudinal axis during reciprocating movement in the cylinder head bore. When this tappet is so arranged in the cylinder head that its longitudinal axis is inclined with respect to the vertical, the inlet opening for the hydraulic oil may migrate between a highest position and a lowest position. Even when the inlet opening has reached its lowest position, the inner oil reservoir of the clearance compensation element remains completely filled with a minimum amount when the combustion engine is shut down because the transfer opening, which connects the inner oil reservoir with the outer oil reservoir, is located at its highest point since in this design the port of the oil channel and the transfer opening oppose each other diametrically.
Thus, in view of the fact that the transfer opening as outlet of the inner reservoir occupies its highest point when the inlet opening is at its lowest point, oil is prevented from flowing out of the inner reservoir. However, in this disposition, the hydraulic oil may flow back at least partially from the outer oil reservoir, which surrounds the inner oil reservoir, via the port, the oil channel and the inlet opening into the supply conduit of the cylinder head. When the internal combustion engine is started again, the partially emptied outer oil reservoir of each cup-shaped tappet must therefore be filled first before the tappet exhibits its even operating behavior.